I taught all my babies sign language, starting when they are about 6 months old. I would say and do the sign, then take their hands and show them how. Eventually they would start doing it. I did more, please, food/eat, drink/cup, play, ball, all done and thank you. And with Mackenzie we did milk and bird. There may have been one or two more. But those are the ones that Mackenzie will still do, and she says the word when she signs it.
It is so wonderful to teach a baby to sign because then I know what they want long before they can verbally say it. It makes life easier.
A friend of mine is writing a paper on teaching babies to sign and had asked me to take some pictures of Mackenzie signing. These were the only ones I was able to get out of her on this day. She is become quite stubborn lately, kind of like her momma. :)